Manual transmission with a gearshift locking mechanism and method

ABSTRACT

A manual transmission with a gearshift locking arrangement includes a rail having a shifter having a slot between forward and rear ears of the shifter, the rail being movable between rail forward and rear positions. The manual transmission with a gearshift locking arrangement also includes forward and rear engagement members disposed at positions corresponding to the rail forward and rear positions. A shift lever is also provided, an engaging portion of the shift lever being adapted to be disposed in the slot, the shift lever being adapted to move the rail between the rail forward and rear position, the engaging portion being engageable with the forward engagement member when the rail is in the rail forward position and the engaging portion being engageable with the rear engagement member when the rail is in the rail rear position.

BACKGROUND AND SUMMARY

The present invention relates generally to manual transmissions and,more particularly, to manual transmissions having gearshift lockingarrangements.

Unintended disengagement in a manual transmission can result from shiftlever inertia forces causing the transmission to disengage from theselected gear position or from a combination of forces both internal tothe transmission as well as external. The lever inertia forces usuallyresult from traversing uneven terrain or from power train excitationcausing excessive motion of the gear shift lever. Internal forces can bethe result of manufacturing deficiencies or unequal load sharing withinmulti counter shaft units which is a common construction feature oftoday's heavy duty truck transmissions.

Unintended disengagement can be source of operator irritation, not tomention more serious concerns regarding safe vehicle operation. Over theyears various types of locking devices have been employed in attempts toovercome these problems. Such locking devices are usually confined tomodifying the jaw clutch components which are used to engage aparticular gear to the transmission main or output shaft to produce alocking effect. This can be accomplished by tapering the engaginginternal and external teeth to produce a dovetail joint type ofconnection which results in an axial force between the two which causesthem remain engaged. While this is effective, the magnitude of theengaging force is dependent upon the load on the power train. Underheavy loads the engaging force is greater. Under light loads theeffectiveness of the engaging force is diminished and therefore cannotalways be employed to overcome disengagement problems under all types ofconditions. Other types of tooth modifications have been utilized overthe years but have met with mixed success or created other problems suchas durability or manufacturing issues and for those reasons thesesolutions are not widely employed.

Attempts have been made to control the shift lever inertia forces butthese usually interfere with the ability to shift the transmissionresulting from the addition of friction or damping forces which must beovercome when shifting from gear to gear.

It is desirable to provide a gearshift locking arrangement that issimple in construction and that minimizes interferences with use of thegearshift.

In accordance with an aspect of the present invention, a manualtransmission with a gearshift locking arrangement comprises a first railhaving a first shifter having a first slot between first forward andrear ears of the first shifter, first forward and rear engagementmembers being provided on the first forward and rear ears of the firstshifter, a second rail having a second shifter having a second slotbetween second forward and rear ears of the second shifter, and a shiftlever, an engaging portion of the shift lever being movable between thefirst slot and the second slot, the shift lever being adapted to movethe second rail between a second rail forward and rear position when theengaging portion is in the second slot, the engaging portion beingengageable with the first forward engagement member when the second railis in the second rail forward position and the engaging portion beingengageable with the first rear engagement member when the second rail isin the second rail rear position.

In accordance with another aspect of the present invention, a shift railassembly for a gearshift mechanism comprises a shift rail, and a shiftermounted on the shift rail, the shifter comprising forward and rear earsdefining a slot for receiving a portion of a gearshift lever, andforward and rear engagement members on the forward and rear ears forengaging an engagement portion of the gearshift lever.

In accordance with yet another aspect of the present invention, a methodof operating a gearshift mechanism comprises moving an engaging portionof a shift lever between a first slot in a first shifter of a firstrail, the first slot being disposed between first forward and rear earsof the first shifter, and a second slot in a second shifter of a secondrail, the second slot being disposed between second forward and rearears of the second shifter, using the shift lever, moving the secondrail one of forwardly and rearwardly relative to the first rail, and,when the second rail is moved forwardly, engaging with the engagingportion a first forward engagement member provided on the first forwardear of the first shifter and, when the second rail is moved rearwardly,engaging with the engaging portion a first rear engagement memberprovided on the first rear ear of the first shifter.

In accordance with yet another aspect of the present invention, a manualtransmission with a gearshift locking arrangement comprises a railhaving a shifter having a slot between forward and rear ears of theshifter, the rail being movable between rail forward and rear positions,forward and rear engagement members disposed at positions correspondingto the rail forward and rear positions, and a shift lever, an engagingportion of the shift lever being adapted to be disposed in the slot, theshift lever being adapted to move the rail between the rail forward andrear position, the engaging portion being engageable with the forwardengagement member when the rail is in the rail forward position and theengaging portion being engageable with the rear engagement member whenthe rail is in the rail rear position.

BRIEF DESCRIPTION OF THE DRAWINGS

The features and advantages of the present invention are well understoodby reading the following detailed description in conjunction with thedrawings in which like numerals indicate similar elements and in which:

FIGS. 1A-1I schematically show a manual transmission with a gearshiftlocking arrangement in different positions according to an embodiment ofthe present invention;

FIG. 2 shows a gearshift pattern of the type usable with a gearshiftlocking arrangement such as is shown in FIGS. 1A-1I;

FIG. 3 schematically shows a manual transmission with a gearshiftlocking arrangement according to another embodiment of the presentinvention;

FIG. 4 schematically show a manual transmission with a gearshift lockingarrangement according to yet another embodiment of the presentinvention;

FIG. 5 is a schematic, partially cross-sectional side view of a shifttower portion of a gearshift locking arrangement according to anembodiment of the present invention;

FIGS. 6A-6B are schematic, partially cross-sectional end views of aportion of a gearshift locking arrangement according to an embodiment ofthe present invention.

DETAILED DESCRIPTION

A manual transmission 21 with a gearshift locking arrangement is shownin FIGS. 1A-1I. The transmission 21 comprises what shall be denominatedas a first rail 23, sometime referred to as a shift rod, having whatshall be denominated as a first shifter 25. The first shifter 25 has afirst slot 27 between first forward and rear ears 29 and 31,respectively, of the first shifter. First forward and rear engagementmembers 33 and 35, respectively, are provided on the first forward andrear ears 29 and 31 of the first shifter 25. A second rail 37 having asecond shifter 39 with a second slot 41 between second forward and rearears 43 and 45, respectively, of the second shifter is also provided. Itwill be appreciated that substantially all components of the manualtransmission 21 except those described herein for locking the gearshiftin position can be of a conventional type. As a result, the manualtransmission 21 according to the present invention is believed to berelatively simple to provide and to use.

The transmission 21 also comprises a shift lever 47 (FIG. 5) having anengaging portion 49 (shown in phantom in FIGS. 1A-1I) that is movablebetween the first slot 27 and the second slot 41. An illustrativeembodiment of the manual transmission 21 with a gearshift lockingarrangement is shown in FIGS. 1A-1I whereby the shift lever 47 can beoperated to move shift between five forward gears and one rear gear of avehicle according to a shifting pattern P such as is shown in FIG. 2. Itwill be appreciated, however, that the manual transmission with agearshift mechanism can be used in conjunction with transmissions havingdifferent shifting patterns and different numbers of gears. For example,FIG. 3 shows a manual transmission 121 with a gearshift lockingarrangement with two shift rails 123 and 137. As seen in FIG. 4, thegearshift locking arrangement according to an aspect of the presentinvention could also be used with a transmission 221 having only asingle shift rail 223, such as where an engaging portion 249 is disposedin or movable into a slot 227 in a shifter 225 and engages withengagement members 255 and 257 mounted to some structure, notnecessarily another shifter.

Referring for purposes of discussion to the embodiment of FIGS. 1A-1I,the shift lever 47 is adapted to move the second rail 37 between asecond rail forward position, as seen in FIG. 1B, and a second rail rearposition, as seen in FIG. 1C, when the engaging portion 49 is in thesecond slot 41. The second rail forward position and the second railrear position might correspond, for example, to gears 1 and 2 of thetransmission. The engaging portion 49 of the shift lever 47 can beengageable with the first forward engagement member 33 when the secondrail 37 is in the second rail forward position (FIG. 1B) and theengaging portion can be engageable with the first rear engagement member35 when the second rail is in the second rail rear position (FIG. 1C).As seen in the figures, the first forward and rear engagement members 33and 35 can comprise protrusions and the engagement portion 49 on theshift lever can comprise a recess 50 for receiving the protrusions. Ofcourse, as one of various possible alternatives, the engagement portionon the shift lever can comprise a protrusion and the engagement memberson the ears of the shifter can comprise recesses for receiving theprotrusion. It will be appreciated that a variety of structures canaccomplish the function of engaging the engaging members with theengaging portion.

When the engaging portion 49 is engaged with an engaging member 33 or35, the transmission 21 will tend to stay in the gear corresponding tothe position to which the shift lever 47 has moved the engaging portion.A biasing member 51 can be provided for urging the engaging portion 49into engagement with either of the first forward or rear engagementmembers 33 or 35. The biasing member 51 can comprise what shall bedenominated a piston member disposed in the second slot 41. The termpiston member will be understood to comprise a variety of structuresadapted to contact the engaging portion 49 in order to urge the engagingportion toward an engaging member and is does not necessarily require apiston head or other structure commonly associated with pistons, and maycomprise or consist essentially of structures such compressibleresilient members such as springs, and piston or piston-like membersassociated with pneumatic, hydraulic, or electromagnetic drivers.

As seen in FIGS. 1D and 1E, the shift lever 47 is adapted to move thefirst rail 23 between a first rail forward (FIG. 1D) and a rear (FIG.1E) position when the engaging portion 49 is in the first slot 27.Second forward and rear engagement members 55 and 57 can be provided onthe second forward and rear ears 43 and 45 of the second shifter 39. Theengaging portion 49 can be adapted to engage with the second forwardengagement member 55 when the first rail 23 is in the first rail forwardposition (FIG. 1D) and the engaging portion can be adapted to engagewith the second rear engagement member 57 when the first rail is in thefirst rail rear position (FIG. 1E).

As seen in the embodiment shown in FIG. 3, in some circumstances, abiasing member 151 can be provided in the first slot 127 for urging theengaging portion 149 into engagement with either of the second forwardor rear engagement members 155 or 157. As the embodiment shown in FIGS.1A-1I will ordinarily permit the engaging portion 49 to pass entirelythrough the slot 27 in the first shifter 25, another arrangement may beused as it may be inconvenient to arrange a biasing member 51 of thetype that can be disposed in the second slot 41 for biasing the engagingportion. FIG. 5 shows a shift lever 47 pivotably mounted in a shifttower 59 about a pivot point 61. The engaging portion 49 is disposed atthe bottom of the shift lever 47.

As seen in FIGS. 6A and 6B, arrangements such as a detent arrangementassociated with the first shifter 25 can be used for retaining theengaging portion 49 in engagement with either of the second forward orrear engagement members 55 or 57. The illustrated detent arrangementincludes a recess or notch 63 in the bottom of the engaging portion andan essentially upside-down “W”-shaped leaf spring 65 or similarlyresilient member defining left and right protrusions 67 and 69,respectively, secured to the shifter 25. When a driver wishes to retainthe engaging portion 49 in engagement with either of the second forwardor rear engagement members 55 or 57, the driver can depress the leafspring 65 so that the left protrusion 67 is received in the notch 63 inthe bottom of the engaging portion. The protrusions 67 and 69 and notch63 can be sized so that, when a protrusion is received in the notch, theprotrusion can be moved out of the notch, and the engaging portion canbe moved out of engagement with the second forward or rear engagementmember 55 or 57, only by positive application of force by the driver todisengage the protrusion and notch.

The manual transmission 21 of FIGS. 1A-1I also comprises a third rail 71on a right side of the first rail 23, the second rail 37 being disposedon a left side of the first rail. The third rail 71 has a third shifter73 having a third slot 75 between third forward and rear ears 77 and 79of the third shifter. The first rail has first forward and rearengagement members 33, 33′ and 35, 35′ on left and right sides of thefirst forward and rear ears 29 and 31 of the first shifter 25. Theengaging portion 49 of the shift lever 47 is movable between the firstslot 27 and the third slot 75. The shift lever 47 is adapted to move thethird rail 71 between a third rail forward (FIG. 1H) and rear (FIG. 1I)position when the engaging portion 49 is in the third slot 75. Theengaging portion 49 is engageable with the right-side first forwardengagement member 33′ when the third rail 71 is in the third railforward position (FIG. 1H) and the engaging portion engageable with theright-side first rear engagement member 35′ when the third rail is inthe third rail rear position (FIG. 1I).

The shift lever 47 is adapted to move the first rail 23 between thefirst rail forward (FIG. 1D) and rear (FIG. 1E) position when theengaging portion 49 is in the first slot 27. In addition to the secondforward and rear engagement members 55 and 57 provided on the secondforward and rear ears 43 and 45 of the second shifter 39, third forwardand rear engagement members 81 and 83 can be provided on the thirdforward and rear ears 77 and 79 of the third shifter 73. When theengaging portion 49 moves the first rail 23 to the first rail forwardposition the engaging portion can be engaged with either one of thesecond forward engagement member 55 (FIG. 1D) and the third forwardengagement member 81 (FIG. 1F) and, when the engaging portion moves thefirst rail to the first rail rear position, the engaging portion can beengaged with either one of the second rear engagement member 57 (FIG.1E) and the third rear engagement member 83 (FIG. 1G).

When a driver wishes to retain the engaging portion 49 in engagementwith either of the third forward or rear engagement members 81 or 83,the driver can depress the leaf spring 65 so that the right protrusion69 is received in the notch 63 in the bottom of the engaging portion(shown in phantom in FIG. 6B). The protrusions 67 and 69 and notch 63can be sized so that, when a protrusion is received in the notch, theprotrusion can be moved out of the notch, and the engaging portion canbe moved out of engagement with the second forward or rear engagementmember 55 or 57, only by positive application of force by the driver todisengage the protrusion and notch.

The manual transmission 21 with a gearshift locking arrangement shown inFIGS. 1A-1I can be used in conjunction with a gearshift pattern P asshown in FIG. 2. When the gearshift 47 (FIG. 5) is in the N positionshown in FIG. 2, the engaging portion 49 can be in the position shown inFIG. 1A. When the gearshift 47 is in the “1” position, e.g., first gear,in FIG. 2, the engaging portion 49 can be in the second rail forwardposition shown in FIG. 1B. When the gearshift 47 is in the “2” position,e.g., second gear, in FIG. 2, the engaging portion 49 can be in thesecond rail rear position shown in FIG. 1C. When the gearshift 47 is inthe “3” position, e.g., third gear, in FIG. 2, the engaging portion 49can be in the first rail forward position shown in FIG. 1D or 1F. Whenthe gearshift 47 is in the “4” position, e.g., fourth gear, in FIG. 2,the engaging portion 49 can be in the first rail rear position shown inFIG. 1E or 1G. When the gearshift 47 is in the “5” position, e.g., fifthgear, in FIG. 2, the engaging portion 49 can be in the third railforward position shown in FIG. 1H. When the gearshift 47 is in the “R”position, e.g., reverse gear, in FIG. 2, the engaging portion 49 can bein the third rail rear position shown in FIG. 1I.

Another embodiment of a manual transmission 121 with a gearshift lockingarrangement is shown in FIG. 3 and can include a first rail 123 having afirst shifter 125 having a first slot 127 between first forward and rearears 129 and 131 of the shifter, with the rail being movable betweenfirst rail forward and rear positions. A second rail 137 has a secondshifter 139 with a second slot 141 between second forward and rear ears145 and 145. First forward and rear engagement members 133 and 135 canbe provided, usually on the first forward and rear ears 129 and 131, atpositions corresponding to second rail forward and rear positions, andsecond forward and rear engagement members 155 and 157 can be provided,usually on the second forward and rear ears, at positions correspondingto first rail forward and rear positions.

A shift lever having an engaging portion 149 can be adapted to bedisposed in either the first or second slot 127 or 141 and the shiftlever can be adapted to move the first or second rails between the firstand second rail forward and rear positions when in the first or secondslots, respectively. The engaging portion 149 can be engaged with thesecond forward engagement member 155 when the first rail 123 is in thefirst rail forward position and the engaging portion can be engaged withthe second rear engagement member 157 when the first rail is in thefirst rail rear position. The engaging portion 149 can be engaged withthe first forward engagement member 133 when the second rail 137 is inthe second rail forward position and the engaging portion can be engagedwith the first rear engagement member 135 when the second rail is in thesecond rail rear position. Usually, when the engaging portion 149 is inone of the first and second rail forward or rear positions, the manualtransmission will be in one of four working gears and, when the engagingportion is in between any of the rail forward or rear positions, such asis shown in FIG. 3, the manual transmission can be in a neutral gear. Abiasing member 151 can be provided in the slots 127 and 141 to keep theengaging portion 149 in engagement with the one of the forward and rearengagement members 133 and 135 or 155 and 157.

FIG. 4 shows another manual transmission 221 with a gearshift lockingarrangement. The manual transmission 221 comprises a rail 223 having ashifter 225 having a slot 227 between forward and rear ears 229 and 231of the shifter. The rail 223 is movable between rail forward and rearpositions which will ordinarily correspond to working gear positions.Forward and rear engagement members 255 and 257 disposed at positionscorresponding to the rail forward and rear positions. The forward andrear engagement members 255 and 257 can be mounted on any suitablestructures. A shift lever with an engaging portion 249 that is adaptedto be disposed in the slot 227 can be provided to move the rail 223between the rail forward and rear position. The engaging portion 249 canbe engaged with the forward engagement member 255 when the rail 223 isin the rail forward position and the engaging portion can be engagedwith the rear engagement member 257 when the rail is in the rail rearposition. A biasing member 251 can be provided in the slot 227 to keepthe engaging portion 249 in engagement with the one of the forward andrear engagement members 255 and 257.

It will be appreciated that the present invention is not limited togearshift mechanisms having one, two, or three shifter rails and thatthe present invention has application in gearshift mechanisms having anynumber of shifter rails.

In a method of operating a gearshift mechanism 21 according to anembodiment of the present invention as shown in FIGS. 1A-1I, an engagingportion 49 of a shift lever 47 is moved between a first slot 27 in afirst shifter 25 of a first rail 23, the first slot being disposedbetween first forward and rear ears 29 and 31 of the first shifter, anda second slot 41 in a second shifter 39 of a second rail 37, the secondslot being disposed between second forward and rear ears 43 and 45 ofthe second shifter. When the engaging portion 49 is in the second slot41, using the shift lever 47, the second rail 37 can be moved eitherforwardly and rearwardly relative to the first rail 23. When the secondrail 37 is moved forwardly, the first forward engagement member 33provided on the first forward ear 29 of the first shifter 25 can beengaged with the engaging portion 49 and, when the second rail is movedrearwardly, the first rear engagement member 35 provided on the firstrear ear 31 of the first shifter can be engaged with the engagingportion. The engaging portion 49 can be retained in the engagement withthe first forward or rear engagement member 33 or 35 by means such as abiasing member 51 that urges the engaging portion to stay in engagementwith the engagement member.

Similarly, using the shift lever 47, when the engaging portion 49 is inthe first slot 27, the first rail 23 can be moved either forwardly orrearwardly relative to the second rail 37. When the first rail 23 ismoved forwardly, the second forward engagement member 55 provided on thesecond forward ear 43 of the second shifter 39 can be engaged with theengaging portion 49 and, when the first rail is moved rearwardly, thesecond rear engagement member 57 provided on the second rear ear 45 ofthe second shifter can be engaged with the engaging portion.Alternatively, using the shift lever 47, when the engaging portion 49 isin the first slot 27, the first rail 23 can be moved either forwardly orrearwardly relative to the third rail 71. When the first rail 23 ismoved forwardly, the third forward engagement member 81 provided on thethird forward ear 77 of the third shifter 73 can be engaged with theengaging portion 49 and, when the first rail is moved rearwardly, thethird rear engagement member 83 provided on the third rear ear 79 of thethird shifter can be engaged with the engaging portion. When engagedwith second or third forward or rear engagement members, the engagingportion 49 can be retained in engagement by any suitable arrangementsuch as the detent arrangement shown in FIGS. 6A-6B provided by theW-shaped leaf spring 65 on the first shifter 25 and the notch 63provided in the engaging portion.

Similarly, using the shift lever 47, when the engaging portion 49 is inthe third slot 73, the third rail 71 can be moved either forwardly orrearwardly relative to the first rail 23. When the third rail 71 ismoved forwardly, the first forward engagement member 33′ provided on theright side of the first forward ear 29 of the first shifter 25 can beengaged with the engaging portion 49 and, when the third rail is movedrearwardly, the first rear engagement member 35′ provided on the rightside of the first rear ear 35′ of the second shifter can be engaged withthe engaging portion. The engaging portion 49 can be retained in theengagement with the first forward or rear engagement member 33′ or 35′by means such as a biasing member 51 that urges the engaging portion tostay in engagement with the engagement member.

Ordinarily, in all embodiments, once the transmission is locked in gearby moving the engaging portion of the shift lever into a slot on a railand moving the rail forwardly or rearwardly, and the engaging portionengages with an engagement member, a conventional interlock mechanism(not shown) is used to prevent movement of the other rails. Since theinterlock prevents the rail of the adjacent shifter from moving, as longas the lever is engaged with the pin, the transmission will remain ingear.

While engagement between engagement members and the engaging portion ofthe shift lever has been described in conjunction with protrusions andrecesses, it will be appreciated that the protrusions and recesses maybe of the size that do not require substantial driver effort todisengage. For example, the protrusions and recesses may be providedwith sloped sides to facilitate engagement and disengagement when adriver pulls the gearshift lever backward or pushes the gearshift leverforward. Similarly, the retention force provided by the W-shaped leafspring and recess arrangement contemplated as one means for retaining agearshift engaging portion in engagement with engagement members willordinarily be of a magnitude that is relatively easily overcome by adriver to permit easy engagement and disengagement. How much drivereffort is appropriate to overcome a retention force will ordinarily varyfrom vehicle to vehicle, often depending upon factors such as theintended use of the vehicle. Obviously, the retention forces shouldordinarily be sufficient to prevent disengagement of the gearshiftduring normal intended operations of the particular vehicle.

In the present application, the use of terms such as “including” isopen-ended and is intended to have the same meaning as terms such as“comprising” and not preclude the presence of other structure, material,or acts. Similarly, though the use of terms such as “can” or “may” isintended to be open-ended and to reflect that structure, material, oracts are not necessary, the failure to use such terms is not intended toreflect that structure, material, or acts are essential. To the extentthat structure, material, or acts are presently considered to beessential, they are identified as such.

While this invention has been illustrated and described in accordancewith a preferred embodiment, it is recognized that variations andchanges may be made therein without departing from the invention as setforth in the claims.

What is claimed is:
 1. A manual transmission with a gearshift locking arrangement, comprising: a first rail having a first shifter having a first slot between first forward and rear ears of the first shifter, first forward and rear engagement members in the form of one of protrusions and protrusion receiving recesses being provided on the first forward and rear ears of the first shifter; a second rail having a second shifter having only a single slot consisting of a second slot between second forward and rear ears of the second shifter; and a shift lever, an engaging portion of the shift lever being movable between the first slot and the second slot, the shift lever being adapted to move the second rail between a second rail forward and rear position when the engaging portion is in the second slot, the engaging portion comprising at least one of a protrusion receiving recess and a protrusion for engaging with the first forward engagement member when the second rail is in the second rail forward position and with the first rear engagement member when the second rail is in the second rail rear position; and at least one of a compressed resilient member, hydraulic pressure, pneumatic pressure, and an electromagnet provided to urge the engaging portion into engagement with either of the first forward or rear engagement members.
 2. The manual transmission with a gearshift locking arrangement as set forth in claim 1, comprising a piston member disposed in the second slot, the at least one of the compressed resilient member, hydraulic pressure, pneumatic pressure, and electromagnet being arranged to urge the piston against the shift lever.
 3. The manual transmission with a gearshift locking arrangement as set forth in claim 1, wherein the shift lever is adapted to more the first rail between a first rail forward and a rear position when the engaging portion is in the first slot.
 4. The manual transmission with a gearshift locking arrangement as set forth in claim 3, comprising second forward and rear engagement members provided on the second forward and rear ears of the second shifter, the engaging portion being engageable with the second forward engagement member when the first rail is in the first rail forward position and the engaging portion being engageable with the second rear engagement member when the first rail is in the first rail rear position.
 5. The manual transmission with a gearshift locking arrangement as set forth in claim 4, comprising at least one of a compressed resilient member, hydraulic pressure, pneumatic pressure, and an electromagnet provided to urge the engaging portion into engagement with either of the first forward or rear engagement member and at least another one of a compressed resilient member, hydraulic pressure, pneumatic pressure, and an electromagnet provided to urge the engaging portion into engagement with either of the second forward or rear engagement members.
 6. The manual transmission with a gearshift locking arrangement as set forth in claim 4, comprising a detent arrangement for retaining the engaging portion in engagement with either of the second forward or rear engagement members.
 7. The manual transmission with a gearshift locking arrangement as set forth in claim 6, wherein the detent arrangement comprises a resilient member associated with the first slot and adapted to engage with a notch in the shift lever.
 8. The manual transmission with a gearshift locking arrangement as set forth in claim 1, comprising a third rail on a right side of the first rail, the second rail being disposed on a left side of the first rail, the third rail having a third shifter having a third slot between third forward and rear ears of the third shifter, wherein the first rail has first forward and rear engagement members on left and right sides of the first forward and rear ears of the tint shifter, and the engaging portion of the shift lever being movable between the first slot and the third slot, the shift lever being adapted to move the third rail between a third rail forward and rear position when the engaging portion is in the third slot, the engaging portion being engageable with the right-side first forward engagement member when the third rail is in the third rail forward position and the engaging portion being engageable with the right-side first rear engagement member when the third rail is in the third rail rear position.
 9. The manual transmission with a gearshift locking arrangement as set forth in claim 8, wherein the shift lever is adapted to move the first rail between a first rail forward and a rear position when the engaging portion is in the first slot.
 10. The manual transmission with a gearshift locking arrangement as set forth in claim 9, comprising second forward and rear engagement members provided on the second forward and rear ears of the second shifter, and third forward and rear engagement members provided on the third forward and rear ears of the third shifter, the engaging portion being engageable with at least one of the second forward engagement member and the third forward engagement member when the first rail is in the first mil forward position and the engaging portion being engageable with at least one of the second rear engagement member and the third rear engagement member when the first rail is in the first rail rear position.
 11. The manual transmission with a gearshift locking arrangement as set forth in claim 10, comprising a detent arrangement for retaining the engaging portion in engagement with any of the second forward or rear engagement members and the third forward or rear engagement members.
 12. The manual transmission with a gearshift locking arrangement as set forth in claim 11, wherein the detent arrangement comprises a resilient member associated with the first slot and adapted to engage with a notch in the shift lever.
 13. The manual transmission with a gearshift locking arrangement as set forth in claim 1, wherein the at least one of the protrusion receiving recess and the protrusion engage with the first forward engagement member when the second rail is in the second rail forward position and with the first rear engagement member when the second rail is in the second rail rear position while the engaging portion is in the second slot.
 14. A method of operating a gearshift mechanism, comprising: moving an engaging portion of a shift lever between a first slot in a first shifter of a first rail, the first slot being disposed between first forward and rear ears of the first shifter, and a second slot in a second shifter of a second rail, the second slot being disposed between second forward and rear ears of the second shifter and the second shifter having only a single slot consisting of the second slot, the engaging portion comprising at least one of a protrusion receiving recess and a protrusion; using the shift lever, moving the second rail one of forwardly and rearwardly relative to the first rail; and when the second rail is moved forwardly, engaging with the engaging portion a first forward engagement member provided on the first forward ear of the first shifter and, when the second rail is moved rearwardly, engaging with the engaging portion a first rear engagement member provided on the first rear ear of the first shifter the forward engagement member, the rear engagement member being in the form of one of protrusions and protrusion receiving recesses for engaging with the engaging portion, by urging the engaging portion into engagement with either of the first forward or rear engagement members with at least one of a compressed resilient member, hydraulic pressure, pneumatic pressure, and an electromagnet.
 15. The method as set forth in claim 14, comprising, using the shift lever, moving the first rail one of forwardly and rearwardly relative to the second rail; and when the first rail is moved forwardly, engaging with the engaging portion a second forward engagement member provided on the second forward ear of the second shifter and, when the first rail is moved rearwardly, engaging with the engaging portion a second rear engagement member provided on the second rear ear of the second shifter.
 16. The method as set forth in claim 14, wherein the at least one of the protrusion receiving recess and the protrusion engage With the first forward engagement member when the second rail is in the second rail forward position. and with the first rear engagement member when the second rail is in the second rail rear position while the engaging portion is in the second slot. 